This is a Bioengineering Research Partnership between UMass Medical School and Lockheed-Martin Corporation. It is aimed at developing and evaluating a new high resolution flat panel mammographic imager with a variable pixel size (40 microns and 80 microns) using tiled charged-coupled devices (CCD). The detector will cover an area essentially the same as the sensitive area of a conventional mammographic cassette. The specific hypotheses are: (a) the new imager will exhibit better detective quantum efficiency (DQE) than current screen-film technology. (b) Unlike current screen-film, the system will exhibit higher dynamic range. (c) The spatial resolution will be higher than current flat-panel imaging systems due to the smaller pixel size and 100 percent fill factor. (d) The contrast will be significantly better than existing screen-film systems resulting in better visualization of breast anatomy at a reduced radiation dose to the patient due to the improved DQE. (e) A well-designed mammographic system driven in an optimized acquisition mode will replace screen-film systems for full-breast mammographic imaging. Preliminary computational and experimental studies suggest that a CCD flat panel detector of this type is feasible. The experimental plan calls for comprehensive evaluation of the characteristics of the detector and evaluation of the system though objective and universally accepted metrics such as the spatially dependent modulation transfer function and DQE. The applicants report experience with the 100 micron pixel GE clinical evaluation prototype in a screening population, which appears to demonstrate equivalency for cancer detection with similar sensitivities. However, there are concerns about of the more subtle forms of calcifications such as punctate and amorphous. When calcium is seen the edge sharpness does not appear to have the same sharpness as that of spot film views. These problems may be related to the relatively large pixel size (100 microns) of the detector. The applicants propose to develop and evaluate the next generation of high resolution digital mammography with high spatial resolution and without the detrimental loss in the signal-to-noise ratio, which is common with the older generation, which uses demagnifying fiberoptics. The proposed prototype using an array of seamlessly tiled CCDs coupled to a structured CsI:TI scintillator by a non-tapering fiberoptic plate will deliver the highest resolution than any other flat panel mammographic detector.